I got introduced to BOTBUILDER from one of the links shared in hacker-news.
Microsoft released version 3 APIs and SDK with performance improvements and new features. Now Skype Bots are integrated in to it.
1. Developer resources
2. Do I Need to be aware of c#? Currently Bot Framework supports Node.js and C#.
3. You can publish your Bot service on any hosting server not just only on Azure. For testing you can publish it locally and test it with the help of Latest Bot Emulator.
4.
5. It has Rest API which allows your bot to send and receive messages to channels configured in the Bot Framework Developer Portal.
https://docs.microsoft.com/en-us/bot-framework/rest-api/bot-framework-rest-overview
Currently WhatsApp not supporting Bots.